Stress, allostatic load and mental health in Indigenous Australians.

The aim of this narrative review was to demonstrate how the notion of allostatic load (AL) relates directly to the mental health disparities observed between Indigenous and non-Indigenous Australians. We also endeavored to synthesize the results of the limited number of studies examining stress and AL in Indigenous Australians in order to explore the potential public health benefits of the AL concept. A range of literature examining health inequalities, psychosocial determinants of mental illness and AL was explored to demonstrate the applicability of stress biology to the significant mental health burden faced by Indigenous Australians. Furthermore, all original studies indexed in MEDLINE that provided quantitative data on primary stress biomarkers in Indigenous Australians were selected for review. Evidence of hypothalamic-pituitary-adrenal axis dysregulation and increased AL is apparent even in the handful of studies examining stress biomarkers in Indigenous Australians. Urinary, salivary, hair and fingernail cortisol, hair cortisone, urinary epinephrine, heart rate variability and the cortisol awakening response are all AL parameters which have been shown to be dysregulated in Indigenous Australian cohorts. Furthermore, associations between some of these biomarkers, self-perceived discrimination, exposure to stressful life events and symptoms of psychiatric disorders in Indigenous Australians have also been demonstrated. The continued assessment of AL biomarkers and their relationship with past traumas, lifetime stressors and socio-economic factors amongst Indigenous Australians is important to addressing the mental health this population. Measurement of AL biomarkers in a culturally appropriate manner may lead to more targeted preventative measures, interventions and policies, which mitigate the effects of stress at both the individual and societal level.

Translational profiling of stress-induced neuroplasticity in the CA3 pyramidal neurons of BDNF Val66Met mice.

Genetic susceptibility and environmental factors (such as stress) can interact to affect the likelihood of developing a mood disorder. Stress-induced changes in the hippocampus have been implicated in mood disorders, and mutations in several genes have now been associated with increased risk, such as brain-derived neurotrophic factor (BDNF). The hippocampus has important anatomical subdivisions, and pyramidal neurons of the vulnerable CA3 region show significant remodeling after chronic stress, but the mechanisms underlying their unique plasticity remain unknown. This study characterizes stress-induced changes in the in vivo translating mRNA of this cell population using a CA3-specific enhanced green fluorescent protein (EGFP) reporter fused to the L10a large ribosomal subunit (EGFPL10a). RNA-sequencing after isolation of polysome-bound mRNAs allows for cell-type-specific, genome-wide characterization of translational changes after stress. The data demonstrate that acute and chronic stress produce unique translational profiles and that the stress history of the animal can alter future reactivity of CA3 neurons. CA3-specific EGFPL10a mice were then crossed to the stress-susceptible BDNF Val66Met mouse line to characterize how a known genetic susceptibility alters both baseline translational profiles and the reactivity of CA3 neurons to stress. Not only do Met allele carriers exhibit distinct levels of baseline translation in genes implicated in ion channel function and cytoskeletal regulation, but they also activate a stress response profile that is highly dissimilar from wild-type mice. Closer examination of genes implicated in the mechanisms of neuroplasticity, such as the NMDA and AMPA subunits and the BDNF pathway, reveal how wild-type mice upregulate many of these genes in response to stress, but Met allele carriers fail to do so. These profiles provide a roadmap of stress-induced changes in a genetically homogenous population of hippocampal neurons and illustrate the profound effects of gene-environment interactions on the translational profile of these cells.

Stress-induced structural plasticity of medial amygdala stellate neurons and rapid prevention by a candidate antidepressant.

The adult brain is capable of adapting to internal and external stressors by undergoing structural plasticity, and failure to be resilient and preserve normal structure and function is likely to contribute to depression and anxiety disorders. Although the hippocampus has provided the gateway for understanding stress effects on the brain, less is known about the amygdala, a key brain area involved in the neural circuitry of fear and anxiety. Here, in mice more vulnerable to stressors, we demonstrate structural plasticity within the medial and basolateral regions of the amygdala in response to prolonged 21-day chronic restraint stress (CRS). Three days before the end of CRS, treatment with the putative, rapidly acting antidepressant, acetyl-l-carnitine (LAC) in the drinking water opposed the direction of these changes. Behaviorally, the LAC treatment during the last part of CRS enhanced resilience, opposing the effects of CRS, as shown by an increased social interaction and reduced passive behavior in a forced swim test. Furthermore, CRS mice treated with LAC show resilience of the CRS-induced structural remodeling of medial amygdala (MeA) stellate neurons. Within the basolateral amygdala (BLA), LAC did not reduce, but slightly enhanced, the CRS-increased length and number of intersections of pyramidal neurons. No structural changes were observed in MeA bipolar neurons, BLA stellate neurons or in lateral amygdala stellate neurons. Our findings identify MeA stellate neurons as an important component in the responses to stress and LAC action and show that LAC can promote structural plasticity of the MeA. This may be useful as a model for increasing resilience to stressors in at-risk populations.

Age and Alzheimer's disease gene expression profiles reversed by the glutamate modulator riluzole.

Alzheimer's disease (AD) and age-related cognitive decline represent a growing health burden and involve the hippocampus, a vulnerable brain region implicated in learning and memory. To understand the molecular effects of aging on the hippocampus, this study characterized the gene expression changes associated with aging in rodents using RNA-sequencing (RNA-seq). The glutamate modulator, riluzole, which was recently shown to improve memory performance in aged rats, prevented many of the hippocampal age-related gene expression changes. A comparison of the effects of riluzole in rats against human AD data sets revealed that many of the gene changes in AD are reversed by riluzole. Expression changes identified by RNA-Seq were validated by qRT-PCR open arrays. Riluzole is known to increase the glutamate transporter EAAT2's ability to scavenge excess glutamate, regulating synaptic transmission. RNA-seq and immunohistochemistry confirmed an increase in EAAT2 expression in hippocampus, identifying a possible mechanism underlying the improved memory function after riluzole treatment.

Erasure of fear memories is prevented by Nogo Receptor 1 in adulthood.

Critical periods are temporary windows of heightened neural plasticity early in development. For example, fear memories in juvenile rodents are subject to erasure following extinction training, while after closure of this critical period, extinction training only temporarily and weakly suppresses fear memories. Persistence of fear memories is important for survival, but the inability to effectively adapt to the trauma is a characteristic of post-traumatic stress disorder (PTSD). We examined whether Nogo Receptor 1 (NgR1) regulates the plasticity associated with fear extinction. The loss of NgR1 function in adulthood eliminates spontaneous fear recovery and fear renewal, with a restoration of fear reacquisition rate equal to that of naive mice; thus, mimicking the phenotype observed in juvenile rodents. Regional gene disruption demonstrates that NgR1 expression is required in both the basolateral amygdala (BLA) and infralimbic (IL) cortex to prevent fear erasure. NgR1 expression by parvalbumin expressing interneurons is essential for limiting extinction-dependent plasticity. NgR1 gene deletion enhances anatomical changes of inhibitory synapse markers after extinction training. Thus, NgR1 robustly inhibits elimination of fear expression in the adult brain and could serve as a therapeutic target for anxiety disorders, such as PTSD.

Mind the gap: glucocorticoids modulate hippocampal glutamate tone underlying individual differences in stress susceptibility.

Why do some individuals succumb to stress and develop debilitating psychiatric disorders, whereas others adapt well in the face of adversity? There is a gap in understanding the neural bases of individual differences in the responses to environmental factors on brain development and functions. Here, using a novel approach for screening an inbred population of laboratory animals, we identified two subpopulations of mice: susceptible mice that show mood-related abnormalities compared with resilient mice, which cope better with stress. This approach combined with molecular and behavioral analyses, led us to recognize, in hippocampus, presynaptic mGlu2 receptors, which inhibit glutamate release, as a stress-sensitive marker of individual differences to stress-induced mood disorders. Indeed, genetic mGlu2 deletion in mice results in a more severe susceptibility to stress, mimicking the susceptible mouse sub-population. Furthermore, we describe an underlying mechanism by which glucocorticoids, acting via mineralocorticoid receptors (MRs), decrease resilience to stress via downregulation of mGlu2 receptors. We also provide a mechanistic link between MRs and an epigenetic control of the glutamatergic synapse that underlies susceptibility to stressful experiences. The approach and the epigenetic allostasis concept introduced here serve as a model for identifying individual differences based upon biomarkers and underlying mechanisms and also provide molecular features that may be useful in translation to human behavior and psychopathology.

Nondrowning Asphyxia in Veterinary Forensic Pathology: Suffocation, Strangulation, and Mechanical Asphyxia.

Asphyxia in a forensic context refers to death by rapid cerebral anoxia or hypoxia due to accidental or nonaccidental injury. Death due to nondrowning asphyxia can occur with strangulation, suffocation, and mechanical asphyxia, each of which is categorized based on the mechanism of injury. Individuals dying due to various types of asphyxia may or may not have lesions, and even those lesions that are present may be due to other causes. The interpretation or opinion that death was due to asphyxia requires definitive and compelling evidence from the postmortem examination, death scene, and/or history. Beyond the postmortem examination, pathologists may be faced with questions of forensic importance that revolve around the behavioral and physiological responses in animals subjected to strangulation, suffocation, or mechanical asphyxia to determine if the animal suffered. While there is no prescriptive answer to these questions, it is apparent that, because of physiological and anatomical differences between humans and animals, for some mechanisms of asphyxia, consciousness is maintained for longer periods and the onset of death is later in animals than that described for people. Veterinary pathologists must be cognizant that direct extrapolation from the medical forensic literature to animals may be incorrect. This article reviews the terminology, classification, mechanisms, and lesions associated with asphyxial deaths in companion animals and highlights significant comparative differences of the response to various types of asphyxia in animals and people.

Veterinary Forensic Pathology: The Search for Truth.

Veterinary forensic pathology is emerging as a distinct discipline, and this special issue is a major step forward in establishing the scientific basis of the discipline. A forensic necropsy uses the same skill set needed for investigations of natural disease, but the analytical framework and purpose of forensic pathology differ significantly. The requirement of legal credibility and all that it entails distinguishes the forensic from routine diagnostic cases. Despite the extraordinary depth and breadth of knowledge afforded by their training, almost 75% of veterinary pathologists report that their training has not adequately prepared them to handle forensic cases. Many veterinary pathologists, however, are interested and willing to develop expertise in the discipline. Lessons learned from tragic examples of wrongful convictions in medical forensic pathology indicate that a solid foundation for the evolving discipline of veterinary forensic pathology requires a commitment to education, training, and certification. The overarching theme of this issue is that the forensic necropsy is just one aspect in the investigation of a case of suspected animal abuse or neglect. As veterinary pathologists, we must be aware of the roles filled by other veterinary forensic experts involved in these cases and how our findings are an integral part of an investigation. We hope that the outcome of this special issue of the journal is that veterinary pathologists begin to familiarize themselves with not only forensic pathology but also all aspects of veterinary forensic science.

Veterinary Forensic Pathology: Drowning and Bodies Recovered From Water.

Determining the cause of death in animals recovered from bodies of water, swimming pools, or other water-containing vessels is challenging. Animals recovered from water may or may not have drowned. The diagnosis of drowning is usually one of exclusion, requiring information from the crime scene, recovery scene, the medical history or reliable witness accounts. While there are characteristic macroscopic and microscopic lesions of drowning, none are specific and are dependent on the volume and tonicity of the drowning medium. Beyond interpreting the postmortem findings, the court may ask pathologists to comment on the behavioral and welfare implications of drowning. This requires an understanding of the drowning process, which is a complex series of sequential, concurrent, and overlapping cardiorespiratory reflexes, electrolyte and blood gas abnormalities, aspiration, physical exhaustion, and breathlessness eventually culminating in death. This review addresses the mechanisms, lesions, and diagnostic issues associated with drowning in nonaquatic companion animals.

A Survey of Attitudes of Board-Certified Veterinary Pathologists to Forensic Veterinary Pathology.

An electronic survey was conducted to determine the attitudes of veterinary pathologists toward forensic pathology and the adequacy of their training in the discipline. The survey was sent to 1933 diplomates of the American College of Veterinary Pathologists and 311 completed responses were analyzed. Of respondents, 80% report receiving at least 1 type of medicolegal case, with cases from law enforcement received most frequently. Most (74%) of the respondents indicated that their previous training did not prepare them adequately to handle forensic cases and almost half of the respondents (48%) indicated that they needed more training on serving as an expert witness. Relative risk ratios (RRR) and odds ratios (OR) were generated to determine the strength of a statistically significant association. Responses from a free-text entry question determining additional training needs could be grouped into 3 main categories: (1) veterinary forensic pathology science and procedures, (2) documentation, evidence collection and handling, and (3) knowledge of the medicolegal system. Last, a field for additional comments or suggestions regarding veterinary forensic pathology was completed by 107 respondents and many reinforced the need for training in the categories previously described. The survey highlights that a significant proportion of diplomates of the American College of Veterinary Pathologists are currently engaged in veterinary forensic pathology but feel their training has not adequately prepared them for these cases. Hopefully, the survey results will inform the college and residency training coordinators as they address the training requirements for an important emerging discipline.